Combined pump and centrifugal separator



March 17, 1942. E. H. CARRUTHERS 2,276,824

COMBINED PUMP AND CENTRIFUGAL SEPARATOR Filed Sept; 25, 1959 2 Sheets--Sheet 1 5 g 1' 'f\ g \3 *3 i *4 a 4 v (E INVENTOR. jzemmrazrluz era%z'sATTORNEYS to a source of use.

Patented Mar. 17, 1942 COMBINED PUMP AND CENTRIFUGAL SEPARATOR EbenHunter Carruthers, Seneca Falls, N. Y., assignor to Goulds Pumps, Inc.,Seneca. Falls, N. Y., a corporation of New York Application September23, 1939, Serial No. 296,269

16 Claims.

My invention relates to a combined pump and centrifugal separator.

An object of my invention is to provide a combined pump and centrifugalseparator which may be economically manufactured, and which is efficientin operation. 7

Another object of my invention is to provide in a system wherein aliquid is continuously reused and is subject to contamination duringuse, improved and more efiective means for removing the contamination.

A further object of my invention is to provide in a system wherein aliquid is continuously reused and is subject to contamination duringuse, means for automatically removing the contaminating materials fromthe liquid by centrifugal force and without requiring any attention onthe part of the operator.

My invention further contemplates an improved coolant system for amachine tool, such as a grinder, wherein means are provided forautomatically removing impurities from the system, such as metalparticles, grit and dirt, which tend to accumulate in the coolant.

Other objects and advantages of my invention will be more particularlypointed out in the claims and will appear from the followingdescription, when taken in connection with the accompanying drawings, inwhich:

Fig. 1 is aview partly in section and partly diagrammatic, showing thecoolant system of my invention as applied to a grinder;

Fig. 2 is a vertical sectional view taken through the casing of thecombined pump and centrifugal separator of my invention with the partsthereof in their normal coolant pumping position;

F g. 3 is a view similar to Fig. 2 with the parts in the position whichthey occupy when impurities are discharged from the unit; and

Fig. 4 is a sectional view showing a somewhat modified form of myinvention.

The system and the combined pump and centrifugal separator of myinvention may be employed wherever impurities in a liquid of differentspecific gravity than the liquid are to be removed from the liquid, andthe liquid is to b pumped The system and apparatus have beenparticularly designed for use in. supplying clean, grit-free coolant toa machine tool. While the apparatus of my invention may be applied to anumber of uses, and the system is not limited to the application hereindisclosed, I have shown and described my combined pump and centrifugalseparator and the system of my invention as applied to a grinder forsupplying a clean grit-free coolant thereto.

The grinder, in the coolant supply system of which my invention may beemployed, has been shown somewhat diagrammatically in Fig. l andincludes a foundation or frame ll upon which is mounted, as indicated atl2, 8. motor [3. The motor is adapted to drive a grinding wheel H whichmay be of any suitable type. For the purpose of supplying a coolant tothegrinder a conduit system, generally indicated by the numeral I6,having a discharge spout or coolant nozzle [1, is provided. The nozzleis adapted to direct the coolant onto the work to be ground andpreferably at the meeting point between the grinding wheel and the workfor the purpose of preventing the work and the grinding wheel fromoverheating.

The coolant may be any suitable liquid, such for example as oil, or anyspecial coolant liquid preparation such as are well known in the machinetool art. The coolant is confined by a shield l8 and by portions of theframe ll, so that it drops by gravity to a tank or coolant sump iii. Ifdesired, a strainer or screen of any suitable type may be employedthrough which the coolant flows to remove large metal chips,

particularly in case the invention is applied to a lathe or other typesof cutting, reaming, boring, or surfacing machine tools. The coolant isnaturally contaminated during the grinding process by fine particles ofmetal and by particles of the grinding wheel which are carried in thecoolant to the sump. In the case of other machine tools the coolant maycontain metal chips some of which are too fine to be removed by flar ngthe coolant through the screen as above mentioned.

In most of the arrangements with which I am familiar, the coolant iscontinually reused, without removing these particles, by pumping thecoolant from the sump back through the conduit system I6. No attempt,other than settling, is made to remove the grit and metal particles andthe coolant is merely replaced with fresh, clean coolant when it becometoo contaminated for further use. The contamination of the coolantsupplied through the conduit system occurs rather rapidly, particularlywhen the impurities are of such character that they will be held insuspension in the coolant and will not settle out in the coolant sumpl9.

In most cases, in order to replace the coolant, which has performed itsfunction of cooling the work and the grinding wheel, as rapidly aspossible with fresh coolant, it is desirable that the coolant besupplied through the nozzle under an appreciable pressure. When thecoolant is highly contaminated with grit and metal particles, theimpingement of these particles on the work causes an abrasive action,which is particularly undesirable in fine machining or grindingoperations. Moreover, the particles may lodge between the grinding wheeland the work and score the work.-

In some installations, where the expense is justified and the characterof the work requires, the coolant from a number of machines may becollected and run through a centrifuge, or other means of removingimpurities, and the coolant after being cleaned may be then returned tothe individual machines for reuse. Insofar as I am aware, however, withthe exception of inadequate filtering systems, no one has heretoforeprovided apparatus of reasonable cost adapted to be applied to a singlemachine for automatically and continuously removing impurities such asdirt, grit and metal particles from the coolant circulated to themachine so that the machine would be at all times supplied with cleancoolant.

I have provided a single unit which serves the function of not onlypumping the coolant to the point of use, but also automatically removesdint, grit, and metal particles fromthe coolant so that only cleancoolant is supplied through the nozzle l1. In Fig. 1 I.have shown thecombined pump and centrifuge of my inventionas supported in the sump bya pedestal 25 with the unit preferably emersed in the coolant so that itis at all times primed. However, instead of the unit being mounted withthe coolant at the level indicated at A, the coolant may be at the levelindi cated by B so that the pump creates a sub-atmospheric pressureadapted to draw the coolant into the unit. Moreover, if desired, theunit may be mounted on the outside of the tank with a suction pipe onthe inside thereof to conduct fluid to the unit.

As shown more clearly in Fig. 2, the unit comprises a casing 25 into achamber 21 of which coolant is drawn either through ports 28 or througha pipe connection 29. Extending into the casing 26 through its upper endis a shaft 3| adapted to be driven by a motor 32 (Fig. 1) carried on amotor support or adapter 33 mounted on the casing, as shown at 34. Apacking gland provided with suitable packing 35 is employed to preventleakage .of air into the casing at this point. Mounted on the end of theshaft which projects into the casing 28 is a rotor, which is indicatedas a whole by the numeral 31. The rotor has incorporated therein acombined pumping and separating unit as will presently appear. While Ihave shown a separate motor for driving the rotor, it would be possibleto suitably gear the shaft 3| to the motor I3 of the machine tool sothat the machine tool and the rotor would be driven together. Thismight, in some cases, be a desirable arrangement because, as will laterbe explained, it is preferable that the rotor be stopped when themachine tool is stopped.

The rotor 31 has an upper or pump part 38 which is rigidly keyed to theshaft, as shown at 39, and which engages a shoulder 4| provided on theshaft. The upper part 38 has vanes 42 and is somewhat similar inconstruction to a conventional centrifugal pump impeller. The pump part38 has an entrance or impeller eye 43 for liquid, adjacent its centralportion and encircling the shaft, from which the blades or vanes 42extend outward and toward the periphery in any manner well known in theart of centrifugal pumps. While I have shown a pump 01 the conventionalcentrifugal type and I prefer this construction because of itsrelatively low cost and the ease and compactness with which it may becombined with a centrifugal separator, other types of pumps might beemployed.

Preferably integrally formed with the lower side of the pump part 38 isa conical skirt 44 which forms the upper half of a separating andcleaning chamber, indicated by the numeral 45. The lower half of theseparating or cleaning chamber is formed by a lower part 41 which has asubstantially conically shaped wall 48 terminating in a cylindricalportion 48. The lower part 41 of the rotor is provided with a hubsection 5| which is connected by webs 52 to the conically shaped wall48. The lower part 41 of the rotor 31 is movable along the shaft withrespect to the upper part or pump section 38. This is accomplished byslidably keying, as shown at 53, the hub section 5| with respect to theshaft. A

spring 54 having one end confined by the pumppart 38 and the other endexerting a downward pressure on the lower part 41 normally urges thelower part 41 in a downward direction, as viewed in Fig. 2. Downwardmovement of the lower part 41 is limited by an annular part 58 engaginga washer 51 backed by a nut 58 threaded to the end of the shaft. Thecylindrical part 48 defines a suction opening 59 which communicates withthe chamber 21. i.

It' will b noted that the webs 52 are of substantia1 area and extendfrom the inner portions of the suction opening 59 outward and upwardtoward the separating and cleaning chamber. When the rotor is operatingthese webs act in a manner similar to that of the blades of acentrifugal pump and cause the coolant to be discharged into theseparating chamber under pressure. The pump action of these webs is notentirely necessary when the pump part 38 is employed. By increasing thearea and pump effect of these webs it might be possible to eliminate thepump part 38. However the particular arrangement shown is of decidedadvantage both in enabling a rather large separation space with a givensize of rotor and in developing a relatively high pressure at thecoolant nozzle l1.

It will now be appreciated that when the rotor is operated, the suctiondeveloped by the centrifugal pump, aided to a certain extent by the webs52, draws liquid into the chamber 21 through the suction opening 59through the separation chamber 48 and into the eye of the centrifugalpump impeller. During the period when the liquid is in or passingthrough the separation chamber 48, it is acted upon by centrifugalforces so that the grit, dirt, and metal particles which are heavierthan the coolant, are thrown outward by the centrifugal forces developedin the chamber and accumulate in the space adjacent the point 6|. Therotor is operated at sufllcient speed to retain the heavier particlesagainst the walls of the separation space while the centrifuged coolantpasses to the eye of the centrifugal pump.

For the purpose of increasing the effectiveness of separation, caused bycentrifugal force developed in the separation chamber 48, there may beprovided either a vane or disc type flow distributor. Either of theseconstructions is well known in the art of centrifugal separators andneed not be further described. As shown in the drawings, I have provideda disc type of flow distributor which comprises a plurality of discs 82,which are perforated and mounted in spaced relation on the hub It willbe noted that the separating action takes place with the liquid underpressure which aids in thoroughly wetting the particles, which otherwisemight float and be carried through with the coolant.

Formed in the casing is a volute 63 for the reception of liquiddischarged from the vanes of the centrifugal pump, and formed in thelower part of the casing is a second volute 64 for the re-. ception ofmaterial discharged from the separation chamber 46, as will be presentlydescribed. A sealing ring 66 mounted in the casing. is effective tomaintain a differential in pressure between the suction opening 59 andthe space 61 surrounding the rotor. It will be noted that the space 61surrounding the rotor is in open communication with the volute 63through the channel 68 so that the pressure developed in the volute 63by the pump is effective throughout the chamber 61 surrounding the rotor31. Also formed in the casing is a passage 69 adapted to receive a pipeconnection II for the discharge of clean coolant free of grit, dirt andmetal particles from the casing and a passage 12 adapted to receive apipe connection I3 for the discharge of grit, dirt, and metal particleswith suflicient coolant to wash out these particles as will laterappear.

When the'pump is operating to deliver liquid to the nozzle [1, thepressure built up by the centrifugal pump is effective throughout thechamber 61 surrounding the rotor to maintain the lower part 41 of therotor in engagement with the pump part 38' against the action of thespring 54 and against the internal pressure within the bowl. Thepressure retaining the separable portions of the rotor in engagement maybe regulated as desired by throttling the pump discharge. Th pressureemployed is sufficient to maintain a seal at the point 14, the adjacentsurfaces of the two rotorparts being preferably accurately machined atthese points. Thus while the motor 32 is driving the rotor, coolant isbeing continuously supplied to the nozzle and the heavier impurities arecollecting on the walls of the separation chamber 46.

As shown in Fig. 1, the pipe connection Il may be connected to aflexible hose I6 which is part of the conduit Hi. The other end of thehose is connected to a pipe 11 which is preferably pivoted, as shown at18, to a support to permit adjustment of the point of application of thestream of coolant issuing from the nozzle l1. A valve 19, controlled bya handle 80, is provided in the pipe 11 for controlling the flow ofcoolant.

The pipe 73 is connected to a pipe 82 having a check valve 8| thereinand the pipe 82 is connected to a valve body 83. The valve is preferablysimilar to that shown in Fig. 4 and comprises a stem 84 protruding fromthe valve body to permit manual actuation of the valve. Upon the lowerend of the steina valve 86 is mounted. Th valve has a solid cylindricalportion 81, adapted to seat as shown at 88, on a seat portion formed inthe valve body. The lower end of the value s provided with a spider orguide arm 89 serving to guide the movements of the valve from the solidline to the dotted line position shown in Fig. 4. When the valve is inthe dotted line position coolant and refuse material are free to flowbetween the arms and'out through a pipe 9!, which empties into askimming tank 92. When the pump is operating the valve is retained in aclosed position by the pressure in the pipe 82. When the pump stops thevalve drops by gravity to an open position. Upon starting the pump againthe velocity and pressure of the liquid cause the valve to move towardits seat. However, before the ,valve can reach its seat, the refusmaterial, together with a portion of the coolant, has been dischargedpast the valve.

While I have shown a valve of what might be termed the impetus type,other types of valvesmight be employed. For example, an ordinary vvalvearranged to operate in synchronism with the discharge of refuse materialfrom the rotor might be employed or a valve with its closure delayed bya dash pot action might be used. I prefer the arrangement shown sincethe operation of the valve and the opening and closing of the rotor areboth dependent upon the pressure within the chamber 61 and the dischargepassage 12 and hence the operation of these parts is synchronized.

Preferably, the skimming tank is provided with a walled compartment 93,having an opening 94. The purpose of the'compartment is to avoid adirect flow of the liquid into the skimming tank so as to avoiddisturbing a settled condition of the refuse material which may exist inthe skimming tank. An overflow spout 96 may discharge into the coolantsump for returning skimmed coolant from the skimming tank 92 to thecoolant sump l9. At intervals in accordance'with the rapidity with whichthe grit, dirt, and metal particles accumulate in th skimming tank, theskimming tank may be cleaned.

In the normal operation of the system clean coolant is continuouslysupplied to the nozzle H, the grit, dirt, and metal particles beingretained in the separation chamber 46. As prethe motor 32 is stopped andpreferably the valve 6 19 is closed. The spring 54 then separates thetwo rotor parts due to the lowered pressure in the chamber 61 and thevalve 81 drops by gravity to the dotted line position shown in Fig. 4.

When the motor is again started, before the rotor has a chance to comeup to speed and pressure is built up in the chamber 61 surrounding therotor, centrifugal force developed in the separation chamber 46 throwsthe refuse material out of the separation chamber. A portionof thecoolant which acts as a flushing agent is thrown out with the refusematerial. The refuse material and flushing coolant flow out through thed'schazge opening 12 and through the valve body 83 into the skimmingtank. As the pressure gradually builds up in the chamber 61 the valve8.! 'is moved towards its seat into the solid line position, shown inFig. 4, and the two parts of the rotor are forced together against theaction of the spring 54. The dirt, grit, and metal particles are thencollected in the separation chamber 46 until the next time the motor isstopped. Up'n again restarting the motor, the refuse material isdischarged into the skimming tank.

It would be entirely possible to discharge refuse material from therotor without stopping and. starting the unit. This may be accomplishedby 'merely reducing the pressure within the chamber 67 (asby opening avalve) to an extent such that it is below the combined forces tending tocause separation of the rotor parts (the spring I8 and the internalpressure within the rotor). However I prefer to stop and start the rotoras this permits a reduction of the pressure in the chamber 81 to that ofatmosphere and thus enables a maximum separation of the rotor parts.

Various arrangements may be employed to control the motor 82. The motor32 may be separately actuated so that once every several hours theoperator may stop and start the motor 82 so as to empty out theaccumulation of refuse material from the separation chamber 48. However,it is preferable that the system be arranged so that the operator doesnot have to perform any conscious operation to cause the discharge ofrefuse material from the separation chamber.

This may be accomplished by connecting the handle 88 of the valve 18 bymeans of a rod 81 to a knife switch 98 which is connected by a circuit89, as shown in the drawings, to both the grinder motor 13, and thecombined pump and centrifugal separator motor 32. With this arrangementeach time the operator wishes to shut down the grinder, as for thepurpose of mounting a different work piece in the machine, it is merelynecessary for him to close the valve 19 so as to cut oil the supply ofcoolant to the nozzle l1, which movement of the handle of the valve 18throws the knife switch open to automatically shut off both motors. Whenthe machine is again started by throwing the handle 88, both motors arestarted and, during the starting of the motor 82, refuse material isdischarged from the separation chamber 48 in the manner previouslydescribed. If a single motor is employed to drive the machine tool andthe combined pump and centrifuge, of course the wiring arrangement abovedescribed need not be employed. Moreover, if desired the handle and theswitch for the motors may be unconnected so that these controls areseparately actuated.

It will be noted that an appreciable pressure is required in thepressure chamber 61 in order to maintain the two halves of the rotor inengagement with each other against the action of the spring 54 andagainst the internal pressure within the rotor. This is accomplished bythrottling the discharge conduit I8, as previously mentioned, so thatthe pressure in the chamber 81 surrounding the rotor, and the pressureholding the valve 81 on its seat, is appreciable. The valve 18 should beclosed each time the motor 82 is stopped so that upon starting the motoragain, the refuse material accumulated in the separation chamber 46 willnot be discharged through the conduit system IS. The check valve 8|,previously mentioned, is employed to prevent the return of any refusematerial in the pipe 82, lying below the valve 81, from flowing backinto the chamber 61 around the rotor and intermingling with cleancoolant.

In Fig. 4 I have shown a somewhat modified form of my invention, themain differences being in the omission of the discs 62, the use of onlya single volute 181, and the use of a single discharge l 02 for both thecoolant and the refuse material. In normal operation clean coolant isdischarged through the discharge I82 past a check valve I83, and into apipe I which is part of the conduit system 18. The check valve ispreferably backed with a relatively heavy pressure spring so that anappreciable pressure is required to open it. When the motor is stopped,the check valve I83 closes and the valve 81 moves from the solid lineposition to the dotted line position shown therein. When the motor isagain 75 started before the pressure has been built up in the dischargeI02 sufliciently to open the check valve I 03, the refuse material,together with a portion of the coolant, discharges through the valve 81which at that tim is in its lower dotted line position. The refusematerial is thus discharged to the skimming tank. As soon as thepressure builds up in the discharge I82 the valve 81 closes and thecheck valve I83 opens. thereby supplying coolant to the nozzle l1. As inthe preferred form of my invention, as soon as the pressure in the spacesurrounding the rotor builds up to the proper amount, the two halves ofthe casing seat against each other, and dirt, grit, and metal particlesaccumulate in the separation space 48 ready to be discharged to theskimming tank the-next time the motor 32 is stopped and started again.

While I have shown separate discharges for the clean coolant and therefuse material, it would be possible to arrange the system so that allof the material is discharged through the coolant nozzle 11. This latterarrangement would, however, be of considerable disadvantage as it wouldbe necessary to turn the nozzle away from the work and discharge therefuse material to a skimming tank or other discharge point each timethe rotor was started. Moreover it would be difficult to flush out theconduit system to clean out refuse material from the conduit. This wouldbe necessary in order to insure the delivery of clean coolant to thework.

While I have shown the preferred forms of my invention, and havedescribed a specific use thereof, it will be appreciated that theapparatus and system have various uses, and that various modificationsand changes may be made in the form and relation of parts withoutdeparting from the spirit of my, invention as set forth in the appendedclaims.

Iclaim:

1. A combined pump and centrifuge comprising, in combination, acentrifugal separator having two separable parts forming a separationchamber, means normally acting to separate said parts,'a pump having astationary casing and a liquid propelling member rotatable therein, saidpump having a discharge connected to a point of use, and a connectionthrough which the pressure of said discharge normally acts to retainsaid separable parts in engagement with each other.

2. A combined pump and centrifuge comprising, in combination, acentrifugal separator having two separable parts forming a separationchamber, means normally acting to separate said parts, a pump having astationary casing and a liquid propelling member rotatable therein, saidpump having a discharge connected to a point of use, a connectionthrough which the pressure of said pump normally acts to retain saidseparable parts in engagement with each other, and means for reducingthe pressure on said parts to automatically separate said parts anddischarge impurities collected in said chamber.

3. A combined pump and centrifuge comprising, in combination, acentrifugal separator having two separable parts forming a separationchamber, means normally acting to separate said parts, a pump having adischarge connected to a point of use, a line having a normally openvalve therein through which impurities from said separator aredischarged, a connection through which the pressure of said pumpnormally acts to keep said separable parts in engagement with each otherand said valve closed, and means for stopping and starting said pump todischarge impurities collected in said chamber through said lineautomatically,

4. In apparatus of the character described, in combination, acentrifugal separator having two separable parts forming a separationchamber, means normally acting to separate said parts, a pump having adischarge connected to a point of use, a line having a pressure actuatedvalve therein through which impurities from said separator aredischarged, a connection through which the pressure of said pumpnormally acts to retain said separable parts in engagement with eachother and said valve closed, and means for stopping and starting saidpump to discharge impurities collected in said chamber through said lineand valve automatically, said pump and said centrifugal separator beingarranged in series with the pump drawing fluid through said chamber.

5. A combined pump and centrifugal separator comprising a casing, ashaft extending into said casing, a pump impeller mounted on said shaftin said casing, a centrifugal separator mounted on said shaft in saidcasing, said centrifugal separator being in two parts one of which ismovable with respect to the other, the discharge of said centrifugalpump being in communication with the casing whereby the pressure thereofis effective to hold said parts together and the discharge of saidcentrifugal separator being in open communication with the suction ofsaid pump.

6. In apparatus of the character described, in combination, acentrifugal separator having a movable part forming a separation chambernormally closed against the discharge of impurities, a pump arranged toforce the fluid through the separation chamber to enable the collectionof impurities in the separation space, a pressure connection connectedto the discharge of the pump for maintaining said part in separationchamber closing position, and means for reducing the pressure in saidconnection to enable movement of said part to separation chamber openingposition.

7. In apparatus of the class described, in combination, a centrifugalseparator having a separation space and including a movable part, apressure pump having its suction connecting directly with the separatingspace and in a manner such that the fluid flows immediately and directlyfrom the separating space to the suction of the pump, the impurities inthe fluid, being removed therefrom as the fluid passes through theseparating space to the pump and a connection communicating with thedischarge of said pump, said connection being arranged with respect tosaid movable part so that the pressure therein normally retains theseparation space closed against the egress of impurities.

8. In apparatus of the character described, in combination, acentrifugal separator having a separation space with an open positionand clcsed position, said space being normally closed against the egressof impurities, a pump having its suction communicating with theseparating space, the impurities in the fluid being removed therefromand retained in the separation space as the fluid passes through theseparating space to the suction of the pump, a connection communicatingwith the discharge of said pump, said connection being arranged withrespect to the separator so that the pressure therein normally retainsthe separation space closed,

9. In apparatus of the character described, in

. combination, a centrifugal separator having separable 'parts forming ya separation chamber, means normally acting to separate said parts, apressure pump having its suction connected directly with the separatingchambe'rand in a manner such that fluid flows immediately and directlyfrom the separation chamber to the suction of the pump, and a connectionthrough which the pressure of said pump normally acts to retain saidseparable parts in engagement with each other against. the action ofsaid'separating means. 1

10. In apparatus of the character described, in combination, acentrifugal separator having, a separation chamber normally closedagainst the egress of impurities, means normally acting to open saidseparation chamber, a pressure pump having its suction connecteddirectly with the separating chamber and in a manner such that purifiedfluid flows immediately and directly from the separation chamber to thesuction of the pump, means including a connection through which thepressure of said pump normally acts to retain said separation chamberclosed, and means for reducing the pressure in said connection to enablethe separation chamber to open automatically and discharge theimpurities collected therein.

11. In an apparatus of the character described, in combination, acentrifugal separator having a separation space, said separation spacehaving an open position in which position the impurities are dischargedand a closed position in which position the impurities are retained insaid separation space, a pressure pump for flowing the liquid to bepurified through said separation space, means including a pressureconnection to the discharge of the pressure pump for retaining theseparation space closed, and means for reducing the pressure in saidpressure connection to enable the separation space to open anddischarge'impurities therefrom.

12. In apparatus of the character described, in combination, acentrifugal separator having a movable part forming a separation chamberclosed against the discharge of impurities, a line having a valvetherein through which impurities from said separator are discharged, a,pump having its suction communication with the separation chamber, aconnection through which the pressure of said pump normally acts toretain said movable part in separation chamber closing position, andmeans for reducing the pressure in said connection to enable movement ofsaid part and the discharge of impurities through said line and valve.

13. In a coolant circulating system for a machine, in combination, acollector into which the coolant flows from the machine, a line having ahand controlled valve therein through which coolant is supplied to themachine, a pump for pumping the coolant through said line, a motor foroperating said pump, a switch electrically connected to said motor,means for actuating the switch to shut off the motor when the handcontrolled valve is operated, means including a centrifugal separatorbetween said collector and said valve for separating impurities fromsaid coolant, and means for discharging impurities from said centrifugalseparator automatically and by centrifugal force upon actuation of saidhand controlled valve.

'14. In apparatus of the character described, in combination, acentrifugal separator having a separation space, a pump connected withthe separation space'for flowing liquid to be purified through saidseparator, means for discharging impurities collected in saidcentrifugal separator comprising a discharge connection having a valvetherein, said valve being normally retained in a closed position by thepressure of said pump.

15. In apparatus of the character described, in combination, acentrifugal separator having separable parts forming a separation space,a 10 pump connected with the separation space for flowing liquid to bepurified through said separation space, a connection through which thepressure 01 said pump acts to normally maintain said separable parts ina closed position, means for discharging impurities collected in saidcentrifugal separator comprising a discharge connection having a valvetherein, said valve nor- 15 parts together.

EBEN HUNTER CARRUTHERS.

